Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR A HIGH EFFICIENCY AND LOW
EMISSION OPERATION OF POWER STATIONS AS
WELL AS FOR STORAGE AND CONVERSION OF
ENERGY
FIELD OF THE INVENTION
The invention relates to a process and a technical device for a better using
of
io heat potentials of a power station and its surrounding as well as connected
plants with it for the reduction of carbon dioxide and NOX emissions in the
environment as well as buffering and reusing of electric energy.
BACKGROUND OF THE INVENTION
The invention is characterized by a complex system of components to find a
solution on the given requests in the energy sector. The plant concept has to
fulfill the following aims in detail:
= Using of electrical overcapacities for foundation of mass storages and its
using for reusing of electrical energy with a high efficiency.
= Creating a power station without emissions,
= Using the expansion energy and the connected different heat potentials with
it for the production of electricity,
= Optimal using low temperature heat capacities for electric power generation,
= Using thermal energy potentials of connected plants for the increasing of
the
electrical efficiency of the whole plant and
= Using thermal energy potentials of surrounding of the plant.
There was not found references in the literature to a similar compact and
cross-
linked plant as invited in spite of an intensive investigation. For this
reason the
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following patent and literature investigations are made separately in the
different fields of the invention.
For the buffering of electrical energy are proved to be pump-fed power
stations
as the most effective methods. Advantageously at this plant technology is the
high efficiency as well as the relatively simple technology. Disadvantageously
at this technology is the high landscape consumption, the limitation to
relatively
few suitable locations and the high water losses by evaporation. For the
storage
of electricity of wind energy the suitable locations are rarely, because the
most
io wind power plants are situated in the plain country or offshore and the
pump-
fed power stations needs a mountainous area. In this situation the advantage
of
the storage will be low, because the long electric conductors and the
unloading
of the networks are not given.
A second possibility is given by development of buffer storages for compressed
air in the underground, which are filled in the USA with overcapacity
electrical
energy and used as a power plant due expansion of the pressured air through a
turbine connected with a generator. Advantageously in this process is the
relatively simple technology and the using the air as working fluid.
2o Disadvantageously are the high energy losses at the compression, the heavy
heat emission and the low efficiency of the process.
Another possibility of the compressed air storage is discussed by using the
compressed air at high pressure as input stream in a burner supported turbo
machine (CAES-concept). In such way the compression of the burning air is not
applicable and the total efficiency is increased.
Further is known and published in the patent specification sheet WO 01/33150
Al that for lowering the production costs of technical gases an continuously
working air separation plant is feed from a storage for compressed air which
is
filled discontinuously with pressured air in relation to a partial aspect of
this
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invention. Because in this case the costs of production of technical gases are
in the focus of the interest, the loss of the compression heat is a usual and
planned energy loss. The energetic use of this heat was outside of discussion.
Other experiments for the using of buffer storages for electrical energy, e.g.
in
batteries, are in development but can not to be used in the process.
The present discussion about the greenhouse effect and climate changes
overcharges from the operators of the power plants an operation without
emissions. Because the energy supplying concept is not to handle without
io fossil fuels, there are many projects, which are dealing with the
separation of
carbon dioxide from the exhaust air and their storage. The separation of
carbon dioxide from exhaust air can be made with the known procedures
condensation, absorption and adsorption. Different scenario will be tested for
the longtime storage in relation to its effects to the environment as well as
of its
ts possible danger potentials for the future. On such way possibilities are
considered for the storage of carbon dioxide in the deep sea, in underground
rock formations and in horizons of former natural gas and oil fields.
There are very different points of views of such methods and the realization
of
20 one of these technologies is not clear. The economy of such procedures is
not
given because the locations of the power plants and the proper locations for
storage of carbon dioxide are distant thousands of kilometers and the carbon
dioxide has to be liquefied or solidified for the transport.
25 For the lowering of the NOx-emissions are known a set of procedures and
state
of the art. A NO,rfree operation is possible in a burning process with pure
oxygen and nitrogen-free accessory gases.
At this time is going a project for burning without nitrogen under the
3o responsibility of Vattenfall in Schwarze Pumpe in Germany. In this case the
separation of the carbon dioxide is taking place by the Oxyfuel-technology.
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From the initiators of the project is judged, that the process is very energy
intensive and had a low efficiency. Besides the it is not easy to find usual
locations for the storage.
Using of expansion energy for the production of energy is known and is putting
into action e.g. at the air separation, the expansion of natural gas, and by
using
of compressed air storages for producing of energy. In the expansion of
natural
gas and compressed air the accompanied high cooling effect is not wanted and
will be prevented, as possible, by preheating of the pressured medium. In air
io separation plants the cooling effect is used for liquefaction and
separation of air
into it components.
Low temperature heat from burning processes is used by two procedures
essentially:
In the ORC (Organic-Rankine-Cycle) - process the heat is took off from a
medium in a heat exchange process and used for the production of vapor, the
vapor is labor-working expanded and driven a generator connected turbine,
therein the expanded vapor is used for preheating of the pressured vapor and
condensed. The heat of condensation is given up to the surrounding.
The efficiency is depending on the temperature of condensation (temperature
of the surrounding) of the used working fluids and the boiling temperature of
nearly 300 K to 625 K. The reachable efficiency of an ORC-plant is given at
the
temperature level of 373 K nearly 6.5 % and the temperature level of 473 K
nearly 13-14 %.
In the Kalina-process heat is took away from the process medium by a heat
exchanger due an ammonia-water-mixture by driving off ammonia. The
3o ammonia vapor is expanded through a turbine and is driving a connected
generator. After them the ammonia is adsorbed in the cooled state in the
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ammonia-water-mixture. In this process is reachable the higher efficiency of
nearly 18 %. Advantageously in this process is the simpler construction of the
plant too and a significant broader range of temperature of the working fluid.
Disadvantageously are the material technical problems caused by the
aggressiveness of the ammonia-water-mixture which will be caused a lower life
time of this few experienced process. A second disadvantage is the possibility
of the emission of the high toxic and environmental endangering ammonia by
legs. Both processes are suiting for using low temperature heat potentials of
the
surrounding too. However the integration of this process is difficult and in
such
io way there is not known practical examples therefore.
Other processes written in patents, are not technically realized at now. It is
used
CO2 as working fluid in all three cases. The inventions writing in the patent
bulletins DE 196 32 019 Cl and EP 0 277 777 B1 are coming closest to the
present invention. Supercritical carbon dioxide is used as working fluid in
the
patent bulletin DE 19632019 Cl for using of low temperature heat in the
temperature range of 40 to 65 C. Into the bargain the pressure is chose in
such way that the critical pressure is not falling short off. Compressing is
taking
place in the supercritical fluid range. The costs of compression for
production of
the higher working pressure are relatively high for this reason.
Disadvantageously is the separation into a working and a heat streaming
circuit
which are coupled by a heat exchanger too. Subsequently are higher heat
losses.
The using a storage of carbon dioxide at the triple point, describing in EP 0
277
777 B1, is a very interest way. The solid liquid carbon dioxide mixture is
produced due a refrigerator by using overcapacities of electrical power. In
times
of energy requirements carbon dioxide is vaporized and used as a carbon
dioxide vapor circuit. On this way a peak shaving of the energy e.g. in the
day
3o night cycle is possible.
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Advantageously at this process is the using of overcapacity energy producing
accumulator of cold, disadvantageously is the use of a relatively high minimum
temperature of more than 200 C in the case of low temperature heat using as
well as the relatively low used working pressure, seen energetically. Further
disadvantageously is the needed gas compression producing the working
pressures. The efficiency of the plant producing electrical energy is
influenced
due both factors too. Calculations show that the efficiency of the plant is
lower
as the present invention.
io In US 4 995 234 and EP 0 277 777 B1 is used a similar basis principle for
the
using of the cold potential of LNG. The liquefaction of carbon dioxide is made
by vaporizing of LNG. The heat is produced by sea water and a gas turbine. At
this process is the using of seawater disadvantageously, advantageously is the
using of LNG, but it limits the operating conditions. These processes are
designing for using the cold potential of LNG for the vaporization and are not
optimal to the power station process.
Likewise a process for using of geothermic heat is working with carbon dioxide
as working fluid, specified in the patent bulletin US 3,875,749. This process
is
working only in the fluid and gas region in such way that the carbon dioxide
as
working fluid takes off in compressed state geothermal heat from an
underground storage and is expanded labor-working in a turbine. After then the
carbon dioxide is compressed new into the fluid range. The complicated
structure of the underground heat exchanger is disadvantageously in this
process and the danger of a geothermal cool down of the surrounding of the
storage is given. Because no parameters in relation to temperature and
pressure are given an exact assessment of the process is not possible.
TASK INVENTION
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Task invention is developing a process for the production of electric energy
in a
with a mixture oxygen and natural gas driven low emission gas turbine and
fluid
turbine power station (GuF- power station) by using of overcapacity electric
energy of the network and using of carbon dioxide as working fluid with
additional using of geothermal potential, with a higher energy efficiency as
before and avoiding known and described previous as well as other defects,
connected with a simple construction based on low material technical effort.
The task is solved by a process and a technical device to realize this process
with a better utilization rate of the heat potentials in operating the power
plant,
io the total avoidance of NO,remission, a significant lower emission of carbon
dioxide in the environment, a good control by the optimal using of given and
changeable ambient temperatures, minimization of the exhaust heat and an
optimal operation in connection with a significant improvement of the
electrical
efficiency as well as the possibility to store the electrical power from
temporary
overcapacities and, after change, to use effective for increasing the
efficiency of
the power plant in the normal operation and preferably for peak load supply.
Different advantageous aspects of other solutions are integrated into the
total
concept in the development of the process, which is leaded to a clean power
plant of a total new construction and operation by the combination of new
technological components. It is used overcharged electrical energy, analogous
to known processes but more effectively, charging high pressure storages of
natural gas, pressed air, and carbon dioxide discontinuously in buffer
storages
in that way that the pressed air is used to produce liquid oxygen in a
continuous
working air separation plant, will be vaporized and used after then together
with
natural gas and carbon dioxide from the underground storage and partial from
the exhaust gas as burning gas mixture at the input pressure of the gas
turbine.
The heat of vaporization of oxygen is used to liquefy the carbon dioxide which
is used as heat carrier and working fluid. The storage of natural gas is
serving
as buffer and as cold source by the expansion of the storage pressure to the
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turbine input pressure and the carbon dioxide storage is the reservoir and
buffer
for carbon dioxide as heat transfer and working fluid for using the thermic
potential of the plant and serving as heat sources too by using of the natural
and stored geothermal potential. The carbon dioxide is filled with cold
liquefied
carbon dioxide and takes off from the surrounding heat, which is renewed by
the compression heat of the other compressed gases as air and natural gas.
Other than by other known solutions the carbon dioxide is used in a fluid form
under high pressure and a normal temperature directly and can be used
immediately for a quick start-up procedure of the gas turbine and the steam
io turbine, driven with carbon dioxide too as heat transfer and working fluid
without
a vaporization process and without other compression procedures. The input of
pure oxygen and natural gas, as well as using of carbon dioxide as heat
transfer and working fluid are allowing the thermodynamic and technologic
effective joint of the unit components to a optimal power plant complex with a
is high electrical effectiveness, without NO,c-emission as well as strong
minimized
emissions of carbon monoxide and carbon dioxide.
The thermal energy of the exhaust gas is taken off by supercritical carbon
dioxide under high pressure as heat transfer fluid in the fluid power plant.
After
20 them the heated supercritical carbon dioxide fluid is labor-producing
expanded
due an expansion turbine connecting with a generator, cooling in this process
and further cooling and liquefying by using a cold source and then compressing
in liquid state to the working pressure and storing in the underground
storage.
As cold sources are used the cooling effects from the expansion of air,
natural
25 gas and carbon dioxide as well as the heat of vaporization of liquid oxygen
and
the cold potential of liquid and vaporized oxygen.
In the process the high effectiveness of the overall power plant is given by
the
chosen combination of the separate units of the plant and the combined using
30 of the different thermodynamic potentials. All of the natural given and
produced
heat and pressure potentials are used producing electrical energy. The exhaust
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air stream, consisting at using clean natural gas from water and carbon
dioxide
only, cooled in the heat exchanger, is partially compressed to an optimal
pressure for the gas turbine, mixed with pure oxygen or rather together with
pure oxygen and natural gas injected into the combustion chamber of the gas
turbine.
In start phase of filling the carbon dioxide storage the whole exhaust gas
stream is compressed in different steps with intermediary drying and cooling
and after them separated. The part of the dried exhaust air, which is not
io returned to the input of the gas turbine, is higher compressed, cooled with
the
exhaust air of the air separation plant and the containing carbon dioxide is
liquefied and pumped by a liquid pump into the underground storage. In case of
the filled underground carbon dioxide storage this process is used for
replacement of losses or for winning of carbon dioxide as product in liquid or
solid state.
EXAMPLES OF APPLICATION
Further advantages are given by the description of an example of application
of
the invention by different temperatures of the using of heat with and without
the
using of a geothermic potential at 301 K as well as the connected figure and
table with different modifications.
In the figure the principle of the construction of the device for the
application of
the process with using the geothermal potential is given schematically.
In the following example of the application the using of the decisive thermal
potential is put into the centre of interest. The corresponding, with the
numbers
20 to 24 characterized duct circuit is marked by increased lines. All of the
other advantages are to understand by specialists direct and without other
commentaries.
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The most important parameters as transferred heats, temperatures and powers
are given in the table in clearly visible form for the two temperatures 423 K
und
473 K. The great advantage of the combination of different heat potentials is
seen in a comparison of the variants A and B according to using the circuit
with
and without geothermal energy.
Temporary not usable electric energy is used for the compression and filling
high pressure storages for natural gas 1, pressured air 2, and carbon dioxide
discontinuously. The high pressure storage for air 2 is used as buffer for a
io continuous working air separation plant 4 for the production of liquid
oxygen,
which is stored in special cryogen containers 5 and, after its vaporization in
an
evaporation device 6, will be feed to the burning process in the gas turbine
7,
in such way that the heat of vaporization of the liquid oxygen is contributed
to
liquefy the carbon dioxide which is used as heat transfer and working fluid in
a
is first heat exchanger 8 at low temperatures. The high pressure storage for
natural gas I is used for stocking and supplying the plant with fuel and the
high
pressure storage of carbon dioxide 3 is used on the one side as buffer for the
supercritical carbon dioxide used as heat transfer and working fluid and has
active tasks in the fluid circuit of the power station for increasing of the
total
2o efficiency by using the waste heat of the power station better for the
production
of electric energy under using of the geothermal energy potential.
Using of pure oxygen and natural gas as well as using of carbon dioxide as
heat transfer fluid are permitting a thermodynamic and technical effective
connection of the separate units of the plant in relation to the total
efficiency,
25 the NOX -avoidance and the significant lowering of the carbon monoxide and
carbon dioxide minimization.
In the vapor circuit unit of the power station consisting of a second heat
exchanger 9, a expansion turbine 10 with partial recompressing of the cooled
3o exhaust gas stream and a with the expansion turbine connected compressor
10a and generator 11 the thermic energy of the exhaust gas stream from the
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exit of the gas turbine 7 is taken off by the high pressure supercritical
carbon
dioxide as heat transfer fluid. After them the heated carbon dioxide stream is
labor-producing expanded due a expansion turbine 10, which is connected with
the generator 11, will be cooled in this process, liquefied by using of a cold
source in a third heat exchangers 12 cooled, in the first heat exchanger 8
liquefied in such way that the temperatures in the first heat exchanger 8 by
help
of a separate oxygen circuit by using of a third heat exchanger 12 and a fifth
heat exchanger 8a is controlled in such way that the carbon dioxide cannot be
crystalline in the first heat exchanger 8, after them in the liquid state
io compressed to the working pressure due a first liquid pump 13 , and again
feed
the carbon dioxide storage 3. As cold sources can be used, depending of the
operation mode of the power plant, the expansion cold energies of the
expansion units 14a und 14b of the reduction of natural gas, the expansion
units of expansion 15a and 15b of pressured air, or the vaporization heat
respectively the warming energy given cold sources and the waste cold of the
air separation unit 4, as well as if required and possible the cold potentials
of
the surrounding. The exhaust gas stream, cooled in the second heat exchanger
9, partial compressed of an optimal pressure for the gas turbine 7 by the
compressor 10a, which is connected with the expansion turbine 10 directly, or
mixed with pure oxygen in a mixing chamber 25 respectively injected together
with natural gas into the gas turbine 7 as cooling and working fluid. Charging
the high pressure storage of carbon dioxide 3 in the commissioning of the
power plant the whole exhaust gas stream is compressed, dried in such way
that it is consisting as pure carbon dioxide nearly, further compressed, by
the
air of an air separation plant 4 in a forth heat exchanger 8b cooled, as a
result
liquefied, in the high pressure container collected and by a second liquid
pump
13a in the high pressure storage for carbon dioxide 3 pumped. At filled
underground storage this way is used too for refilling of losses or for the
production of pure carbon dioxide in liquid or solid state.
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Using of carbon dioxide as heat transfer and working fluid under pressure
specially is advantageously for using of low temperature thermic energy for
their
conversation in electric energy. In this case carbon dioxide is liquefied at
low
temperatures, then compressed in the liquid state to supercritical pressures,
taking off heat in this range, after them labor-working expanded due an
expansion turbine connected with a generator in such way that the turbine is
driving the generator, the carbon dioxide is cooled in this procedure and the
final temperature of the carbon dioxide is set of the wanted pressure for the
liquefaction. After them the carbon dioxide is liquefied at this pressure by a
cold
io source, the heat of condensation is removed, and the following increasing
of
the pressure is made by a liquid pump to the wanted supercritical working
pressure.
The choice of the supercritical region is made for the heat absorption because
the advantageous thermodynamic conditions for the heat exchange in this
region at temperatures, which is of interest for using of low temperature heat
for
producing electrical energy. That is caused by high values of heat capacity,
low
values of viscosity, connected with values of thermal conductivity which are
comparable with the values of steam. The thermodynamic useable range to low
temperatures is limited by the triple point of carbon dioxide at nearly 217 K,
corresponding with a pressure of nearly 0,55 MPa. To above there are no
thermodynamic limits as well as in the temperature and pressure. Limitations
of
other sorts are given for practical and material reasons. Another advantage is
given at the using of carbon dioxide in comparison to the ORC-process
because no additional heat exchanger is necessary and the heat transfer
medium and the working medium are identically in a closed circulatory control
management.
Advantageously is too, that carbon dioxide is using a low environmental
3o dangerous potential and that the availability of carbon dioxide is relative
high.
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In the used process the possibility is consisting too, using big amounts of
car-
bon dioxide to use useful as working fluid connecting with using of geothermal
or ambient heat for increasing of the efficiency of the whole process.
In such way significant advantages are given against the ORC- process and the
Kalina-process.
Other advantages are given by higher efficiencies and the combination with
heat and cold potentials, which are increasing further the effectiveness of
the
whole power station without additional input of fuels. This is being
successful
io using the geothermal potential near the surface of the earth as well as
using the
cold sources which are given in expansion processes particularly to the
expansion of natural gas and pressed air for the liquefaction of carbon
dioxide
The example of application is demonstrating this with a very high electrical
effectiveness.
The process is used advantageously for removing and controlled storage of
carbon dioxide because the big buffer as a contribution against the green
house effect. The device to realize the process is permitting a discontinuous
operation of the power plant with considerable changing conditions and
operations modes without problems in the times of quick start-ups and
adaptations.
An example for the using external heat potentials is given in the table. At a
comparison between example 1 a and 1 b is to see that the using of a
geothermal potential at the temperature of 301 K the effectiveness of the
whole
fluid is increased of nearly 7%.
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Table
Fluid Unit Tempe- Pressure Power Electr. Electr. Net Example
flog rature MPa kW Gross Net Efficiency
K Therm. Electr.
20 423 15
la
10+11 1015,5
21 260 2,0
8+12 -289,5
22 253 2,0
13 -124
23,24 260 15
9 3788
1015,5 890 23,5 %
20 423 15
Ib
10+11 1015,5
21 260 2
8+12 -289,5
22 253 2
13 -124
23 260 15
24 301
9 2922
1015,5 890 30,5 %
20 473 15
Ila
10+11 1721
21 232 0,6
8+12 -4486
22 220 0,6
13 -123
23,24 224 15
19 5598
1721 1599 31,0%
20 473 15
IIb
10+11 1721
21 232 0,6
8+12 -3556
22 220 0,6
13 -123
23 224 15
24 301
9 2442
1721 1599 44,4 %
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